[U-Boot] [PATCH 5/5] Warn when the machine ID isn't passed to an ARM kernel and u-boot is compiled in debug mode. The kernel cannot boot without it.

[Christopher Harvey <charvey@matrox.com>]

On Mon, Jul 04, 2011 at 04:13:49PM -0400, Jason wrote:
> On Mon, Jul 04, 2011 at 02:55:54PM -0400, Christopher Harvey wrote:
> > On Mon, Jul 04, 2011 at 02:08:44PM -0400, Jason wrote:
> > > On Mon, Jul 04, 2011 at 01:45:41PM -0400, Christopher Harvey wrote:
> > > > +	   Hopefully there will never be this many machines. 
> > > > +	   Can't use 0 since 0 is already used as a mach-type. */
> > > > +	gd->bd->bi_arch_number = 0xffffffff; 
> > > >  
> > > >  	gd->bd->bi_baudrate = gd->baudrate;
> > > >  	/* Ram ist board specific, so move it to board code ... */
> > > > diff --git a/arch/arm/lib/bootm.c b/arch/arm/lib/bootm.c
> > > > index 802e833..70b3b76 100644
> > > > --- a/arch/arm/lib/bootm.c
> > > > +++ b/arch/arm/lib/bootm.c
> > > > @@ -113,6 +113,12 @@ int do_bootm_linux(int flag, int argc, char *argv[], bootm_headers_t *images)
> > > >  		printf ("Using machid 0x%x from environment\n", machid);
> > > >  	}
> > > >  
> > > > +#ifdef DEBUG
> > > > +	if(machid==0xffffffff) {
> > > > +	        debug("\nWarning: machid not set! Linux will not finish booting.\n\n");
> > > 
> > > s/finish/start/ ;-)
> > >
> > I'll have to disagree here.  Linux will decompress and some functions
> > will run but it will eventually stop, hence will not finish.
> 
> On further investigation, you're right, it doesn't finish
> starting/booting.  Sorry for the noise.
> 
> > > Also, shouldn't the compile fail in this case (#error)?  Or, at least #warn?
> > >
> > The compiler can't know what machid will be at runtime. Maybe a "would
> > you like to continue?" prompt could work.
> 
> Since the kernel throws a nice fat error message when the MACH_TYPE
> doesn't match what it was compiled for, I don't see the point to adding
> another message at the same point in the development process.

I didn't see that message. Do you know what lines of code in the
kernel print it? Or maybe just the message itself? 
If the kernel can check the value why would it need to be passed 
in the first place?

> Perhaps use the constant CONFIG_MACH_TYPE, set to 0xffffffff.  Each
> board config file sets it to MACH_TYPE_WHATEVER and then you could
> do:
> 
> #if CONFIG_MACH_TYPE == 0xffffffff
> #warning "Machine type not set!  Linux will not finish booting!"
> #endif
> 
> You could use -Werror to fail on such things.  DBGFLAGS in ./config.mk
> might be a good place.
> 
> If the maintainers choose to move to a menuconfig style configuration
> system, this logic could be handled in there (invalid config file).

Right now CONFIG_MACH_TYPE is only used in a few boards and isn't used
in core u-boot code, so I ignored it. I would agree that perhaps
adding a CONFIG_MACH_TYPE to u-boot would be a more elegant solution
than checking to make sure that it is a valid value before boot, but
that would be another patch.

>  
> > > Please take comments with a grain of salt, I'm asking, not telling.  I'm
> > > fairly new to this as well.
> > >
> > I'm happy to clarify. 
> 
> Thanks for exercising my brain before I seek out the beer and
> explosives. ;-)
> 
> Jason.

-Chris